Why are some Parkinson’s disease patients unaware of their dyskinesias?

Objective : To test the hypothesis that anosognosia-for-dyskinesias in Parkinson’s disease (PD) results from a failure to detect discrepancies between intended and actual movement. Background : PD patients often complain of drug-induced dyskinesias (involuntary movements) less than their carers. This remarkable unawareness is an example of anosognosia (i.e., unawareness of deficits associated with an illness). A better understanding of anosognosia-for-dyskinesias in PD is important to understanding the impact of the illness and side effects of treatment. Method : The ability to detect a discrepancy between intended movement and visual feedback about actual ovement was investigated in 6 PD patients with anosognosia-for-dyskinesias, 11 non-anosognosic PD controls with dyskinesias, and 22 healthy volunteers (HVs), using a mirror to reverse the expected visual consequences of an executed movement. Results : Non-anosognosic PD patients and HVs rated mirror-reversed movement as significantly stranger than normal movement (p=.024 and <.001 respectively), whereas PD patients with anosognosia-for-dyskinesias did not (p=.375). Conclusion: The findings support our proposal, in that PD patients with anosognosia-fordyskinesias do not report mirror-reversed movement (in which intentions and visual feedback conflict) as feeling distinct from normal movement.